Sedimentary infill of Early-Middle Jurassic in the southeastern Tarim Basin and its constraints on the evolution of the Altyn Tagh Fault in the Northeast Tibet Plateau

Abstract

The Altyn Tagh Fault (ATF) is the boundary between the Tarim Basin and the Tibetan Plateau, which is crucial for the tectonic evolution and uplift of the Tibetan Plateau. However, the Mesozoic tectonic evolution of the ATF remains controversial. This study reconstructed the Early-Middle Jurassic palaeogeographic pattern of the southeast depression of the Tarim Basin (SDTB) and revealed potential source-sink relationships between the SDTB and its adjacent mountains to constrain the Mesozoic tectonic evolution of the ATF based on sedimentology and provenance analyses. The results indicated that the SDTB was infilled with alluvial fan facies during the Early Jurassic and the late Early Jurassic, giving rise to the braided-river delta to lacustrine facies. During the Middle Jurassic, the lacustrine basin expanded with the wide development of lacustrine facies, and the lacustrine basin contracted and was primarily infilled with braided delta facies in the late Middle Jurassic. The Jurassic sedimentary center, the SDTB situated in front of the Altyn Tagh Mountain and East Kunlun Mountain, played a crucial role in the development of three types of hydrocarbon source rocks: charcoal mudstone, coal beds, and dark mudstone. Combined with seismic reflection data interpretations, the Early Jurassic the STDB is a rift basin that underwent a rift-depression transition in the late Early Jurassic, solidifying the characteristics of the depression basin in the Middle Jurassic. The extensional environment in the SDTB resulted from the tectonic effects of slab break-off following the closure of the Tethys Ocean and the spreading of the distal stress field of the Bangonghu–Nujiang Ocean. The analyses of gravel component and heavy mineral indicated that the Jurassic source of the basin was traced back to the ancestral Altyn Mountains, the East Kunlun Mountains, and the internal palaeo-uplift of the basin, which demonstrated that the SDTB and Western Qaidam Basin (WQB) shared a common lacustrine basin during the Jurassic, suggesting that the ATF did not initiate strike-slip movements during this period. This study significantly enhanced our understanding of the Mesozoic tectonic evolution in Northwest China, providing valuable insights into exploring Mesozoic oil-bearing basins in the northern Tibetan Plateau. Furthermore, it served as a useful reference for constraining the timing of the initial slip of similar plate boundary strike-slip faults.